package top.roadvast.logfilter.service;
/**
 * @Author : JCccc
 * @CreateTime : 2019/7/30
 * @Description : 敏感词过滤器：利用DFA算法  进行敏感词过滤
 **/
 
import top.roadvast.logfilter.util.SensitiveWordInit;

import java.util.HashSet;
import java.util.Map;
import java.util.Set;
 
public class SensitiveFilterService {
 
 
    private Map sensitiveWordMap = null;
 
    // 最小匹配规则
    public static final int MIN_MATCH_TYPE = 1;
 
    // 最大匹配规则
    public static final int MAX_MATCH_TYPE = 2;
 
    // 单例
    private static SensitiveFilterService instance = null;
 
    // 构造函数，初始化敏感词库
    private SensitiveFilterService() {
        sensitiveWordMap = new SensitiveWordInit().initKeyWord();
    }
 
    // 获取单例
    public static SensitiveFilterService getInstance() {
        if (null == instance) {
            synchronized (SensitiveFilterService.class) {
                if (null == instance) {
                    instance = new SensitiveFilterService();
                }
            }
        }
        return instance;
    }
 
    // 获取文字中的敏感词
    public Set<String> getSensitiveWord(String txt, int matchType) {
        Set<String> sensitiveWordList = new HashSet<>();
        for (int i = 0; i < txt.length(); i++) {
            // 判断是否包含敏感字符
            int length = CheckSensitiveWord(txt, i, matchType);
            // 存在,加入list中
            if (length > 0) {
                sensitiveWordList.add(txt.substring(i, i + length));
                // 减1的原因，是因为for会自增
                i += length - 1;
            }
        }
 
        return sensitiveWordList;
    }
 
    /**
     * 替换敏感字字符
     *
     * @param txt 文本
     * @param matchType 匹配类型，最小匹配/最大匹配
     * @param replaceChar 要替换成什么字符
     * @return 替换后的结果
     */
    public String replaceSensitiveWord(String txt, int matchType,
                                       String replaceChar) {
        String resultTxt = txt;
        // 获取所有的敏感词
        Set<String> set = getSensitiveWord(txt, matchType);
        for (String word : set) {
            String replaceString = getReplaceChars(replaceChar, word.length());
            resultTxt = resultTxt.replaceAll(word, replaceString);
        }
        return resultTxt;
    }
 
    /**
     * 获取替换字符串
     *
     * @param replaceChar 替换的字符
     * @param length 长度
     * @return 替换后的字符串
     */
    private String getReplaceChars(String replaceChar, int length) {
        StringBuilder resultReplace = new StringBuilder(replaceChar);
        for (int i = 1; i < length; i++) {
            resultReplace.append(replaceChar);
        }

        return resultReplace.toString();
    }
 
 
    /**
     * 检查文字中是否包含敏感字符，检查规则如下：
     * 如果存在，则返回敏感词字符的长度，不存在返回0
     *
     * @param txt 原始文本
     * @param beginIndex 开始索引
     * @param matchType 匹配规则 最小匹配/最大匹配
     * @return 敏感词字符的长度
     */
    public int CheckSensitiveWord(String txt, int beginIndex, int matchType) {
 
        // 敏感词结束标识位：用于敏感词只有1位的情况
        boolean flag = false;
        // 匹配标识数默认为0
        int matchFlag = 0;
        Map<Object, Object> nowMap = sensitiveWordMap;
        for (int i = beginIndex; i < txt.length(); i++) {
            char word = txt.charAt(i);
            // 获取指定key
            nowMap = (Map) nowMap.get(word);
 
            // 存在，则判断是否为最后一个
            if (nowMap != null) {
 
                // 找到相应key，匹配标识+1
                matchFlag++;
                // 如果为最后一个匹配规则,结束循环，返回匹配标识数
                if ("1".equals(nowMap.get("isEnd"))) {
                    // 结束标志位为true
                    flag = true;
                    // 最小规则，直接返回,最大规则还需继续查找
                    if (SensitiveFilterService.MIN_MATCH_TYPE == matchType) {
                        break;
                    }
                }
            } else {
                // 不存在，直接返回
                break;
            }
        }
        if (SensitiveFilterService.MAX_MATCH_TYPE == matchType) {
            //长度必须大于等于1，为词
            if (matchFlag < 2 || !flag) {        
                matchFlag = 0;
            }
        }
        if (SensitiveFilterService.MIN_MATCH_TYPE == matchType) {
            //长度必须大于等于1，为词
            if (matchFlag < 2 && !flag) {        
                matchFlag = 0;
            }
        }
        return matchFlag;
    }
}